The present invention relates generally to earthworking agricultural implements and more particularly to moldboard plows.
As a plow bottom moves through the soil, the share or business end of the plow penetrates the soil and cuts the furrow slice loose. With continued use, the share eventually becomes worn and must be replaced. Not infrequently, however, the share will break or crack as obstacles in the soil are encountered. To reduce share breakage as obstacles are encountered, trip linkages have been provided which permit the plow to trip or raise and then pass over the obstacles. These linkages often include power reset mechanisms which reorient the plow for reentry into the ground after it has been tripped. Nevertheless, share failure occasionally occurs as a result of the forces which are encountered when the plow bottom is forced back into the ground by such mechanisms. To minimize the expense of replacing shares which fail, detachable share-cutting edges have been provided, see for example U.S. Pat. No. 2,038,340 to Briggs. Such edges, however, still require considerable time to install.
To extend the life of the share and reduce share breakage, the cross sectional thickness has been increased by some manufacturers. See for example the Model HS bottom as used on John Deere plows. When a share is thickened, the upper edge which abuts the moldboard is thicker than the lower edge of the moldboard. Consequently, the frog supporting it was reduced in thickness to drop the surface of the share to the same level as the moldboard or else shims were inserted between the moldboard and frog to raise the moldboard to the level of the share. Either solution was directed towards assuring that a continuously concave soil working surface existed across the moldboard-share joint. To offset the frog thickness beneath the share required additional forging expense and the assembly and replacement expense increased by shimming moldboards during manufacture or share replacement was significant. Further, when a moldboard was shimmed, portions of it were not supported. These portions are then subjected to severe stresses during soil working operation and often cause moldboard failure.